Submission #1102678

#	Time	Username	Problem	Language	Result	Execution time	Memory
1102678		alexdd	Graph (BOI20_graph)	C++17	100 / 100	174 ms	40952 KiB

Graph

#include <bits/stdc++.h>
#pragma GCC optimize("O3,unroll-loops")
using namespace std;
#define int long long
#define double long double
const int INF = 1e14;
int n,m;
double val[100005];
int u[200005],v[200005],s[200005];
vector<pair<int,int>> con[100005];
bool visited[100005];
bool bun;
double cur;
vector<int> aux;
vector<pair<double,int>> v0;
int parte[100005];
void dfs(int nod)
{
    if(parte[nod]==0) v0.push_back({val[nod],nod});
    else v0.push_back({-val[nod],nod});
    aux.push_back(nod);
    visited[nod]=1;
    for(auto [adj,sum]:con[nod])
    {
        if(!visited[adj])
        {
            val[adj] = sum - val[nod];
            dfs(adj);
        }
        else if(val[adj] != sum - val[nod])
            bun = 0;
    }
}
bool isbipartit;
pair<int,int> parent[100005];
int cap1,cap2,scap;
void dfs_bipartit(int nod)
{
    for(auto [adj,c]:con[nod])
    {
        if(parte[adj]==-1)
        {
            parte[adj] = 1-parte[nod];
            parent[adj] = {nod,c};
            dfs_bipartit(adj);
        }
        else if(parte[adj] != 1-parte[nod])
        {
            isbipartit=0;
            cap1 = adj;
            cap2 = nod;
            scap = c;
        }
    }
}
bool verif_bipartit(int nod)
{
    parte[nod]=0;
    isbipartit=1;
    dfs_bipartit(nod);
    if(!isbipartit)
    {
        int cur=cap1;
        double sum=scap,sum2=0;
        int pas=0;
        while(cur!=cap2)
        {
            if(pas==0)
            {
                sum2 += parent[cur].second;
            }
            pas = 1-pas;
            sum += parent[cur].second;
            cur = parent[cur].first;
        }
        sum/=2;
        val[cap2] = sum - sum2;
        bun=1;
        dfs(cap2);
        if(!bun)
        {
            cout<<"NO";
            exit(0);
        }
    }
    return isbipartit;
}
vector<double> possible;
signed main()
{
    ios_base::sync_with_stdio(0);cin.tie(0);
    for(double i=-100;i<=100;i+=0.5)
        possible.push_back(i);
    cin>>n>>m;
    for(int i=1;i<=m;i++)
    {
        cin>>u[i]>>v[i]>>s[i];
        con[u[i]].push_back({v[i],s[i]});
        con[v[i]].push_back({u[i],s[i]});
    }
    for(int i=1;i<=n;i++)
    {
        parte[i]=-1;
        visited[i]=0;
    }
    for(int i=1;i<=n;i++)
    {
        if(!visited[i])
        {
            if(verif_bipartit(i))
            {
                bun=1;
                val[i]=0;
                v0.clear();
                dfs(i);
                if(!bun)
                {
                    cout<<"NO";
                    return 0;
                }
                double mnm=INF,unde;
                for(double x:possible)
                {
                    double cur=0;
                    for(auto [y,id]:v0)
                        cur += abs(y+x);
                    if(cur < mnm)
                    {
                        mnm = cur;
                        unde = x;
                    }
                }
                for(auto [y,id]:v0)
                {
                    if(parte[id]==0) val[id] += unde;
                    else val[id] -= unde;
                }
            }
        }
    }
    cout<<"YES\n";
    for(int i=1;i<=n;i++)
        cout<<val[i]<<" ";
    return 0;
}

Compilation message (stderr)

Graph.cpp: In function 'int main()':
Graph.cpp:136:34: warning: 'unde' may be used uninitialized in this function [-Wmaybe-uninitialized]
  136 |                     else val[id] -= unde;
      |                          ~~~~~~~~^~~~~~~

• Subtask 1: 5 / 5
• Subtask 2: 12 / 12
• Subtask 3: 17 / 17
• Subtask 4: 24 / 24
• Subtask 5: 42 / 42